INTERNAL PAIR DECAY OF GIANT-RESONANCES IN HOT PB-200

Electron-positron pairs with transition energies of less than or equal to 25 MeV emitted during the deexcitation of highly excited Pb-200 pr oduced in the F-19 + Ta-181 reaction were detected in the Stony Brook pair detector in order to study internal pair conversion from giant re sonances in a hot nucleus. The observed kinematic e(+)-e(-)variables s how that the pair decay is overwhelmingly of E1 character. The extract ed transition spectrum confirms the statistical model prediction that the giant dipole resonance in the hot (E(x) = 57 MeV) Pb-200 nucleus d ominates internal pair conversion from 4 to 20 MeV transition energy. E1 pair conversion coefficients extracted from a comparison with avail able gamma spectra obtained in the same reaction show that the point n ucleus and Born approximation can be used for energies above 6.5 MeV e ven in this high-Z nucleus. Results from a search for e(+)-e(-)pairs f rom giant monopole resonances are presented.